Modulation of transient and persistent inward currents by activation of protein kinase C in spinal ventral neurons of the neonatal rat.
Neuronal excitability can be regulated through modulation of voltage threshold (Vth). Previous studies suggested that this modulation could be mediated by modulation of transient sodium currents (I(T)) and/or persistent inward current (PIC). Modulation of I(T) and PIC through activation of protein kinase C (PKC) has previously been described as a mechanism controlling neuronal excitability. We investigated modulation of I(T) and PIC by PKC in neonatal rat spinal ventral neurons. In whole cell voltage clamp, activation of PKC by application of 1-oleoyl-2-acetyl-sn-glycerol (OAG, 10-30 microM) resulted in 1) a reduction of I(T) amplitude by 33% accompanied an increase in half-width and a decrease in the maximal rise and decay rates of the I(T); 2) a reduction of PIC amplitude by 49%, with a depolarization of PIC onset by 4.5 mV. Activation of PKC caused varied effects on Vth for eliciting I(T), with an unchanged Vth or depolarized Vth being the most common effects. In current-clamp recordings, PKC activation produced a small but significant depolarization (2.0 mV) of Vth for action potential generation with an increase in half-width and a decrease in amplitude and the maximal rise and decay rates of action potentials. Inclusion of PKCI19-36 (10-30 microM), a PKC inhibitor, in the recording pipette could block the OAG effects on I(T) and PIC. The ability of serotonin to hyperpolarize Vth was not altered by PKC activation or inhibition. This study demonstrates that activation of PKC decreases the excitability of spinal ventral neurons and that Vth can be modulated by multiple mechanisms.
Dai
Yue
Y
Department of Physiology, University of Manitoba, 745 Bannatyne Ave., Winnipeg, MB, Canada R3E 0J9.
Jordan
Larry M
LM
Fedirchuk
Brent
B
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000831:Animals, Newborn; D002462:Cell Membrane / Q000187:drug effects; D004075:Diglycerides / Q000494:pharmacology; D004594:Electrophysiology; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000201:enzymology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000502:physiology; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology*
D004075:Diglycerides; D004791:Enzyme Inhibitors; D007473:Ion Channels; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D012701:Serotonin; C038237:1-oleoyl-2-acetylglycerol; D011493:Protein Kinase C